why does log a + log b = log (ab)

Let log a be some number A and log b be some number B

now the natural log of something is the equivalent of saying a=e^A and b = e^B

So a*b = e^A * e^B which by rules of indices

 = e^(A+B)

Therefore log(ab) = log(e^(A+B))

= A + B = log a + log b 

RV

Related Maths A Level answers

All answers ▸

How do you solve 3sin2AtanA=2 for 0<A<180?


Simplify the following algebraic fraction; (3x^2 - x - 2) / ((1/2)x + (1/3)).


A curve has equation y = f(x) and passes through the point (4, 22). Given that f'(x) = 3x^2 - 3x^(1/2) - 7, use integration to find f(x), giving each term in its simplest form


x = 3t - 4, y = 5 - (6/t), t > 0, find "dy/dx" in terms of t